U.S. patent number 4,694,709 [Application Number 06/772,427] was granted by the patent office on 1987-09-22 for control of a vehicle automatic transmission.
This patent grant is currently assigned to Mazda Motor Corporation. Invention is credited to Toshiyuki Kikuchi, Koichi Yamamoto.
United States Patent |
4,694,709 |
Kikuchi , et al. |
September 22, 1987 |
Control of a vehicle automatic transmission
Abstract
A vehicle automatic transmission having a torque converter and a
multiple-stage gear mechanism. When the vehicle is stopped and the
shift lever is in the D-range, the gear mechanism is shifted to the
highest gear stage if the vehicle brake is engaged and the engine
is idling, so that transmission of the engine idling vibrations to
the vehicle body can be prevented by the transmission.
Inventors: |
Kikuchi; Toshiyuki
(Higashi-Hiroshima, JP), Yamamoto; Koichi (Hiroshima,
JP) |
Assignee: |
Mazda Motor Corporation
(Hiroshima, JP)
|
Family
ID: |
26505067 |
Appl.
No.: |
06/772,427 |
Filed: |
September 4, 1985 |
Foreign Application Priority Data
|
|
|
|
|
Sep 8, 1984 [JP] |
|
|
59-188666 |
Sep 8, 1984 [JP] |
|
|
59-188667 |
|
Current U.S.
Class: |
477/94; 701/54;
701/62 |
Current CPC
Class: |
F16H
61/20 (20130101); F16H 59/22 (20130101); F16H
59/44 (20130101); F16H 59/54 (20130101); Y10T
477/647 (20150115); F16H 2061/0488 (20130101); F16H
2061/023 (20130101); F16H 2312/02 (20130101); F16H
61/36 (20130101) |
Current International
Class: |
F16H
61/20 (20060101); F16H 61/26 (20060101); F16H
59/54 (20060101); F16H 61/04 (20060101); F16H
59/50 (20060101); F16H 59/44 (20060101); F16H
59/18 (20060101); F16H 59/22 (20060101); F16H
61/36 (20060101); B60K 041/06 () |
Field of
Search: |
;74/865,866
;364/424.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Braun; Leslie
Assistant Examiner: Diehl; Dwight G.
Attorney, Agent or Firm: Fleit, Jacobson, Cohn &
Price
Claims
We claim:
1. A vehicle having vehicle brake means, an engine provided with
engine output control means having an idle position, an automatic
transmission comprising a torque converter having a turbine, a
multiple-stage transmission gear mechanism connected with the
turbine of the torque converter and having a neutral gear stage, a
first gear stage and at least one higher gear stage, gear stage
selecting means for selecting one of the gear stages, and a shift
lever having a neutral range and at least one running range for
operating the gear stage selecting means so that the neutral gear
stage is selected when the shift lever is in the neutral range and
one of the first and higher gear stages is selected when the shift
lever is in the running range, the improvement comprising shift
position detecting means for detecting that the shift lever is in
the running range, engine idle detecting means for detecting that
the engine output control means is in the idle position, vehicle
stop detecting means for detecting that the vehicle is
substantially stopped, vehicle brake detecting means for detecting
that the vehicle brake means is engaged, control means responsive
to output signals from said detecting means to operate the gear
stage selecting means when the shift lever is in the running range
and the vehicle is stopped so that the gear mechanism is shifted to
the higher gear stage in an instance wherein the engine output
control means is in the idle position and the vehicle brake means
is engaged, which vehicle further includes idle up detecting means
for detecting that the engine is operated with an increased idle
speed, said control means including means for prohibiting a shift
up to the higher gear stage when the engine is operated with the
increased idle speed under a condition wherein the shift lever is
in the running range, the vehicle is stopped, the engine output
control means is in the idle position and the vehicle brake means
is engaged.
2. A vehicle in accordance with claim 1 in which said idle up
detecting means is choke switch means which detects that engine
choke valve means is in an operative position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle automatic transmission,
and more particularly to a vehicle automatic transmission having a
hydraulic torque converter and a multiple-stage transmission gear
mechanism connected with the torque converter. More specifically,
the present invention pertains to a control of a vehicle automatic
transmission of the aforementioned type.
2. Description of the Prior Art
In a vehicle having an automatic transmission comprised of a torque
converter and a multiple-stage transmission gear mechanism, a shift
lever is provided for selecting one of an N-range (neutral),
D-range, 2-range, 1-range, R-range (reverse) and P-position
(parking). It has been experienced in this type of vehicle that if
the vehicle is kept stationary with the shift lever positioned in a
running range such as the D-range or the 2-range, the engine idle
vibrations are transmitted through the transmission to the vehicle
body disturbing the riding comfort. In order to solve the problem,
the transmission gear mechanism may be brought into the neutral
position even when the shift lever is in the running range. It
should however be noted that this solution is not satisfactory
because a shifting shock is produced when the shift lever is moved
from the N-range to the running range, such as the D-range, 2-range
and 1-range. This type of shifting shock is sometimes referred to
as the "N-D shock" and caused by the fact that a power transmitting
gear train is established in the transmission gear mechanism
through engagements of appropriate friction members when the shift
lever is actuated, to make it possible to transmit the engine
output power through the gear mechanism to the wheels of the
vehicle. This problem can be solved by having a higher gear stage
such as a third or fourth gear stage to engage, in lieu of making
the gear mechanism neutral, so that the driving torque transmitted
to the driving wheels can be made smaller and the engine idle
vibration transmitted to the vehicle body can therefore be reduced.
Japanese patent application 54-131972 filed on Oct. 12, 1979, and
disclosed for public inspection on May 20, 1981, under the
disclosure number 56-57524 proposes, under a condition wherein the
vehicle is stopped with the shift lever in a running range, to hold
the gear mechanism in the first stage for a predetermined time and
then automatically shift up to a higher stage, such as the third or
fourth gear stage, after the predetermined time. With the control
as proposed by the Japanese patent application, it is possible to
start the vehicle smoothly utilizing the creep phenomenon of the
torque converter within the predetermined time after a vehicle
stop. It is also possible to reduce the engine idle vibrations
transmitted to the vehicle body when the vehicle is kept in the
stopped condition beyond the predetermined time.
It should, however, be noted that the control as proposed by the
Japanese patent application is not satisfactory because the
transmission of the engine idle vibrations cannot be suppressed
during the predetermined time. Further, it becomes impossible to
utilize the creep phenomenon of the torque converter for a smooth
start of the vehicle after the vehicle has been stopped beyond the
predetermined time.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide
vehicle automatic transmission control means wherein the vehicle
body vibrations can be suppressed and simultaneously assuring a
smooth vehicle start.
Another object of the present invention is to provide vehicle
automatic transmission control means of the aforementioned type
wherein the gear mechanism is shifted to a higher gear stage when
the engine output control member is in the minimum output position
and the vehicle brake is engaged.
According to the present invention, the above and other objects can
be accomplished in a vehicle having an engine provided with engine
output control means having an idle position, vehicle brake means,
an automatic transmission comprised of a torque converter, a
multiple stage transmission gear mechanism connected with the
torque converter and having a neutral gear stage, a first gear
stage and at least one higher gear stage, gear stage selecting
means for selecting one of the gear stages, and a shift lever
having a neutral range and at least one running range for operating
the gear stage selecting means so that the neutral gear stage is
selected when the shift lever is in the neutral range and one of
the first and higher gear stages is selected when the shift lever
is in the running range. For that purpose, there are provided shift
position detecting means for detecting that the shift lever is in
the running range, engine idle detecting means for detecting that
the engine output control means is in the idle position, vehicle
step detecting means for detecting that the vehicle is stopped,
brake detecting means for detecting that the vehicle brake means is
engaged. Control means is further provided to receive signals from
the aforementioned detecting means and operate the gear stage
selecting means when it is detected that the shift lever is in the
running range, the vehicle is stopped, the engine output control
means is in the idle position and the vehicle brake mean is
engaged. The control means functions to operate the gear stage
selecting means when the above conditions are met, so that the gear
mechanism is positioned in the higher gear stage.
When it is detected that the brake means is engaged while the
engine is idling, it is judged that the driver is willing to
maintain the vehicle stationary. Therefore, the control means
operates the gear stage selecting means so that the higher gear
stage is maintained. With this control it is possible to suppress
transmission of the engine idling vibrations to the vehicle body.
As soon as the brake means is released, it is judged that the
driver is willing to start the vehicle, so that the gear mechanism
is shifted down to the first gear stage for a smooth vehicle
start.
Thus, according to the present invention, there is provided a
vehicle having vehicle brake means, an engine provided with engine
output control means having an idle position, an automatic
transmission comprising a torque converter having a turbine, a
multiple-stage transmission gear mechanism connected with the
turbine of the torque converter and having a neutral gear stage, a
first gear stage and at least one higher gear stage, gear stage
selecting means for selecting one of the gear stages, and a shift
lever having a neutral range and at least one running range for
operating the gear stage selecting means so that the neutral gear
stage is selected when the shift lever is in the neutral range, and
one of the first and higher gear stages is selected when the shift
lever is in the running range, the improvement comprising shift
position detecting means for detecting that the shift lever is in
the running range, engine idle detecting means for detecting that
the engine output control means is in the idle position, vehicle
stop detecting means for detecting that the vehicle is stopped,
brake detecting means for detecting that the vehicle brake means is
engaged, control means responsive to output signals from said
detecting means to operate the gear stage selecting means when the
shift lever is in the running range and the vehicle is stopped, so
that the gear mechanism is shifted to the higher gear stage when
the engine control means is in the idle position and the vehicle
brake means is engaged. According to the above features of the
present invention, the transmission gear mechanism is shifted down
to the first stage when the vehicle brake means is released. At
this instance, the driving torque transmitted to the driving wheels
is stepwisely increased. This may cause an uncomfortable shock
under certain operating conditions. For example, in the engine
warming up period, or when an engine driven facility such as the
air conditioner is in operation, the engine is being operated at an
increased idle speed so that there is a possibility that the
vehicle starts to run very suddenly beyond the driver's expectation
when the vehicle brake means is released and the gear mechanism is
shifted down to the first stage. In one aspect of the present
invention, therefore, the transmission gear mechanism is held in
the first stage even when the above conditions are met if the
engine is being operated under an increased idle speed.
The above and other objects and features of the present invention
will become apparent from the following description of a preferred
embodiment taking reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatical illustration of a vehicle traction
system in which the present invention is embodied;
FIG. 2 is a sectional view showing an automatic transmission and
its hydraulic control circuit in accordance with one embodiment of
the present invention;
FIG. 3 is a block diagram showing a control unit in accordance with
one embodiment of the present invention;
FIG. 4 is a block diagram showing the details of the idle vibration
suppress circuit;
FIG. 5 is a diagram showing an example of the gear shifting
map;
FIG. 6 is a program flow chart showing the general operation of the
control unit;
FIG. 7 is a flow chart showing the steps of shift-up control;
FIG. 8 is a diagram showing the shift-up map;
FIG. 9 is a flow chart showing the steps of shift-down control;
FIG. 10 is a diagram showing the shift-down map;
FIG. 11 is a flow chart showing the steps of converter lock-up
control;
FIG. 12 is a diagram showing the lock-up map; and,
FIG. 13 is a flow chart showing the operation for suppressing idle
vibrations.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Basic Structure of the Transmission
Referring now to FIG. 2, there is shown an automatic transmission 1
which comprises a hydraulic torque converter 10, a multiple stage
transmission gear mechanism 20, and a planetary gear type
over-drive transmission mechanism 40 arranged between the torque
converter 10 and the multiple stage transmission gear mechanism
20.
The torque converter 10 has a pump 13 connected with an output
shaft 3 of an engine 2 through a drive plate 11 and a converter
casing 12, a turbine 14 provided in the casing 12 to face the pump
13 and a stator 15 disposed between the pump 13 and the turbine 14.
A converter output shaft 16 is connected with the turbine 14. A
lock-up clutch 17 is provided between the converter output shaft 16
and the casing 12, which is connected to the pump 13. The lock-up
clutch 17 is normally engaged with the casing 12 under the pressure
of hydraulic fluid which circulates in the torque converter 10, and
is released by hydraulic pressure, which is drawn to a space
between the casing 12 and the clutch 17 from an external pressure
source.
The muliple stage transmission gear mechanism 20 has a front
planetary gear unit 21 and a rear planetary gear unit 22. The front
planetary gear unit 21 has a sun gear 23 connected with a sun gear
24 of the rear planetary gear unit 22 though a connecting rod 25.
The gear mecahnism 20 has an input shaft 26 connected through a
front clutch 27 with the connecting rod 25, and through a rear
clutch 28 with an internal gear 29 of the front planetary gear unit
21. A front brake 31 is provided between the connecting rod 25 or
the sun gears 23, 24 of the gear units 21 and 22 and a casing 30 of
the transmission. The gear mechanism 20 also has an output shaft 34
connected with a planetary carrier 32 of the front planetary gear
unit 21 and an internal gear 33 of the rear planetary gear unit 22.
The rear planetary gear unit 22 has a planetary carrier 35, and
there are provided between the planetary carrier 35 and the
transmission casing 30 a rear brake 36 and a one-way clutch 37.
The planetary gear type over-drive transmission mechanism 40
includes planetary gears 41a, a planetary carrier 41 rotatably
carrying the planetary gears 41a and connected with the output
shaft 16 of the torque converter 10, a sun gear 42 engaged with the
planetary gears 41a, and an internal gear 43 which is also engaged
with the planetary gears 41a and connected with the sun gear 42
through a direct connecting clutch 44. An over-drive brake 45 is
provided between the sun gear 42 and the transmission casing 30.
The internal gear 43 is connected with the input shaft 26 of the
multiple stage transmission gear mechanism 20.
The multiple stage transmission gear mechanism 20 is of a known
type and can provide three forward driving gear stages and one
reverse stage through selective engagements of the clutches and
brakes. The relationships between the forward gear stages and the
engagements of the clutches and brakes are shown in Table 1,
together with typical values of gear ratios in the gear stages. The
planetary gear type over-drive transmission mechanism 40 connects
the shafts 16 and 26 directly when the direct connection clutch 44
is engaged and the brake 45 is released, and provides an over-drive
connection between the shafts 16 and 26 when the brake 45 is
engaged and the clutch 44 is released. This function is shown in
Table 2 together with typical values of the gear ratios.
TABLE 1 ______________________________________ FRONT REAR FRONT
REAR GEAR GEAR CLUTCH CLUTCH BRAKE BRAKE RA- STAGE 27 28 31 36 TIO
______________________________________ 1 o o 2.841 2 o o 1.541 3 o
o 1.000 ______________________________________
TABLE 2 ______________________________________ DIRECT CONNECT
OVER-DRIVE GEAR CLUTCH BRAKE STAGE 44 45 GEAR RATIO
______________________________________ DIRECT o 1.000 OVER- o 0.720
DRIVE ______________________________________
It will be understood that, by combining the three forward gear
stages in the gear mechanism 20 and the two gear stages in the
over-drive transmission gear mechanism 40, it becomes possible to
obtain six gear stages of different overall gear ratios.
Hydraulic Control Circuit
The above-mentioned automatic transmission is provided with a
hydraulic control circuit as shown in FIG. 2. The hydraulic control
circuit has an oil pump 50 which is driven by the engine output
shaft 3. Hydraulic oil is discharged under pressure from the pump
50 into a pressure line 51. The oil pressure is reduced by a
pressure regulating valve 52 and applied to a select valve 53. The
select valve 53 has a plunger which can be selectively positioned
by means of a shift lever 53a in one of the shift positions 1, 2,
D, N, R and P. When the plunger is positioned in one of the shift
positions 1, 2 and D, the pressure line 51 is communicated with
ports a, b, c of the select valve 53. The port a is communicated
with a hydraulic actuator 28a for the rear clutch 28 through a line
54. When the select valve 53 is positioned in the above mentioned
position, the actuator 28a makes the rear clutch 28 engage. The
port a is also communicated with the left-hand end portion of a 1-2
shift valve 61 having a spool 61a which is now biased rightward in
FIG. 2 under the oil pressure from the port a. The port a is
further communicated with the right-hand end portion of the 1-2
shift valve 61 through a first line 56, the right-hand end portion
of a 2-3 shift valve 62 through a second line 57, and the upper end
portion of 3-4 shift valve 63 through a third line 58. First,
second and third drain lines 66, 67 and 68 are provided in the
first, second and third lines 56, 57 and 58, respectively. These
drain lines 66, 67 and 68 are respectively provided with a first,
second and third solenoid valves 71, 72 and 73 for opening and
closing them. When the port a is communicated with the line 51 and
the solenoid valves 71, 72 and 73 are energized to close the drain
lines 66, 67, 68, the pressure is built up in the first, second and
third line 56, 57, 58.
The port b is communicated with a second lock valve 78 through a
line 80. The oil pressure which is applied from the port b to the
second lock valve 78 acts to bias the spool 78a of the valve 78
downwards. When the spool 78a of the valve 78 is in the lower
position, the line 80 is communicated with the line 79 so that the
oil pressure is introduced into a brake engaging pressure chamber
31a' of an actuator 31a to engage the front brake 31. The port c is
communicated with the second lock valve 78 through a line 81. The
oil pressure which is applied from the port c to the second lock
valve 78 acts to bias the spool 78a of the valve 78 upward. The
port c is also communicated with the 2-3 shift valve 62 through a
pressure line 81a having an orifice check valve 82. The line 81a is
communicated with a line 83 when the spool 62a of the 2-3 shift
valve 62 is moved leftward by the pressure in the second line 57,
which increases upon energizing the solenoid valve 72 in the drain
line 67. The line 83 is communicated through a line 84 with the
releasing pressure chamber 31a" of the actuator 31a. When oil
pressure is introduced into the releasing pressure chamber 31a",
the actuator 31a is moved to release the brake 31 against the
pressure in the engaging pressure chamber 31a'. Further, the
pressure in the line 83 is introduced through a line 85 into the
actuator 27a for the front clutch 27 to make the clutch 27
engage.
The select valve 53 has a port d which is communicated with the
pressure line 51 when the valve 53 is positioned in the position 1.
The port d is communicated with the 1-2 shift valve 61 through a
line 86, and from there with an actuator 36a for the rear brake 36
further through a line 87. When the solenoid valves 71 and 72 are
energized, the spools 61a and 62a of the 1-2 shift valve 61 and the
2-3 shift valve 62 are moved to thereby change the port connections
for engaging appropriate brakes and/or clutches to establish 1-2,
2-3 shifting operations, respectively. The hydraulic control
circuit is also provided with a cut-back balve 98 for making the
oil pressure from the pressure regulating valve 52 stable, a vacuum
throttle valve 96 for varying the line pressure supplied from the
pressure regulating valve 52 through a line 89 according to the
suction pressure in the engine intake passage, and a valve 97 for
backing up the throttle valve 96. The throttle pressure from the
vacuum throttle valve 96 is supplied to a line 95.
Furthermore, this hydraulic control circuit is provided with an
actuator 44a for controlling the clutch 44 and an actuator 45a for
the brake 45 of the planetary gear type over-drive transmission
mechanism 40. The actuator 45a has an engaging pressure chamber
45a' communicated with the pressure line 51 through a line 90. The
brake 45 is operated when the actuator 45a is moved under the
pressure in the line 51. The pressure line 51 is connected through
a line 89 with the 3-4 shift valve 63. When the solenoid valve 73
is energized, the spool 63a of the 3-4 shift valve 63 is moved
downward to communicate the pressure line 51 through the line 89
with a line 91 so that the oil pressure is introduced into the line
91. The oil pressure introduced into the line 91 acts through a
line 92 on a releasing pressure chamber 45a" of the actuators 45a
to release the brake 45, and on the actuator 44a to make the clutch
44 engage.
Still further, the present hydraulic control circuit is provided
with a lock-up control valve 64, which is communicated with the
port of the select valve 53 through a line 59. From the line 59
extends a drain line 69 which is provided with a solenoid valve 74.
When the pressure in the line 59 increases by closing the drain
line 69 with the solenoid valve 74 being energized, the lock-up
control valve 64 has its spool 64a moves upward to cut the
communication between lines 93 and 94 and drain the pressure in the
line 94 so that the lock-up clutch 17 is engaged.
In the above arrangement, the relations of the overall gear ratios
and the operations of the solenoids, the brakes and the clutches
are shown in Table 3.
TABLE 3
__________________________________________________________________________
DIRECT FRONT REAR FRONT CONNECT OVER-DRIVE SOLENOID SOLENOID
SOLENOID CLUTCH CLUTCH BRAKE CLUTCH BRAKE GEAR 71 72 73 27 28 31 44
45 RATIO
__________________________________________________________________________
OFF OFF OFF o o 2.841 ON OFF OFF o o o 1.541 OFF ON OFF o o o 1.000
OFF OFF ON o o 2.046 ON ON OFF o o o 1.000 ON OFF ON o o o 1.110
OFF ON ON o o o 0.720 ON ON ON o o o 0.720
__________________________________________________________________________
It will be understood from Table 3 that six different gear ratios
can be obtained through selective energization of the three
solenoids 71, 72 and 73. Thus, it is possible to selectively
combine the gear ratios to provide a plurality of operating modes
as, for example, shown in Table 4.
TABLE 4 ______________________________________ GEAR POWER NORMAL
ECONOMY ECONOMY STAGE MODE MODE MODE A MODE B
______________________________________ 1 2.841 2.841 2.046 2.046 2
2.046 1.541 1.541 1.541 3 1.541 1.000 1.000 1.110 4 1.000 0.720
0.720 1.000 5 0.720 0.720
______________________________________
In Table 5, there is shown a relationship between the operation of
the solenoid 74 and the torque converter lock-up.
TABLE 5 ______________________________________ SOL 74 Lock-up
______________________________________ ON engage OFF release
______________________________________
General Arrangements
Referring to FIG. 1, it will be noted that an electronic control
unit 100 is provided for controlling the above hydraulic circuit.
The vehicle is provided with a vehicle brake device B which is
actuated by a brake pedal P. For detecting that the brake is
engaged, there is provided a brake pedal switch 114 which closes
when the brake pedal P is depressed. The engine 2 has a throttle
valve 2a which is provided with a throttle position sensor 104. The
throttle valve 2a is actuated by a foot pedal A which is provided
with an engine idle switch 113 adapted to be closed when the pedal
A is released. The turbine 13 of the torque converter 10 is
provided with a turbine speed sensors 103 and the shift lever 53a
is provided with a shift position sensor 105. The signals from the
sensors and switches are applied to the control unit 100, which
then controls the hydraulic circuit in accordance with the
signals.
Control Unit
Referring now to FIG. 3, it will be noted that the control unit 100
includes a shift control circuit 101 and a lock-up control circuit
102, which are connected with the turbine speed sensor 103, the
throttle position sensor 104 and the shift position sensor 105 to
receive a turbine speed signal a, a throttle position signal b and
a shift position signal c. The circuit 101 functions to judge,
based on the input signals a, b and c, whether the engine operating
condition is in the shift-up zone, the shift-down zone or in the
hold zone, referring to the control map shown in FIG. 5. Similarly,
the circuit 102 functions to judge whether the operating condition
is in the lock-up zone or not. The circuit 101 produces shift
signals d.sub.1 through d.sub.4, which respectively correspond to
the first through fourth gear stages. The circuit 102 produces a
lock-up signal e. The outputs for the signals d.sub.1 through
d.sub.3 are applied respectively to one input of AND circuits 106,
107 and 108 and the output for the signal d.sub.4 is applied to one
input of an OR circuit 109. The outputs of the circuits 106 through
109 are applied to a solenoid selecting map 110 which has outputs
f.sub.1, f.sub.2 and f.sub.3 for energizing the solenoids 71, 72
and 73, respectively. The lock-up signal e from the circuit 102 is
applied to the solenoid 74 to control the lock-up clutch 17.
It will be noted in FIG. 3 that the control unit 100 further
includes an idle vibration suppressing circuit 111. As shown in
detail in FIG. 4, the circuit 111 is connected with a D-range
switch 112 which is closed when the shift lever 53a is in the
D-range to produce a D-range signal g, an idle switch 113 which is
closed when the foot pedal A is in the idle position to produce an
idle signal h and the aforementioned turbine speed sensor 103. The
D-range signal g and the idle signal h are applied to an AND
circuit 116. The turbine speed signal a is applied to an F-V
converter 117 in which the signal a is converted into a voltage
signal. The output signal from the F-V converter 117 is applied to
a negative terminal of a comparator 118 to be compared with a
reference signal. The comparator 118 produces an output a' which is
at a high level when the turbine speed is below a predetermined
value, for example, 200 rpm and turns to a low level when the
turbine speed increases beyond a second predetermined value, for
example, 280 rpm. The signal a' from the comparator 118 is also
applied to the AND circuit 116.
In the illustrated embodiment, there is provided a hand brake in
addition to the foot brake B and a hand brake switch 114.sub.2 is
provided so as to be closed when the hand brake is engaged to
thereby produce a hand brake signal i.sub.2. The foot brake switch
114.sub.1 produces a foot brake signal i.sub.1 when closed. The
switches 114.sub.1 and 114.sub.2 are connected with an OR circuit
119, which produces a high level output i when either or both of
the brake signals i.sub.1 and i.sub.2 are produced. The output of
the OR circuit 119 is also applied to the AND circuit 116. The
engine 2 is further provided with a choke valve C which has a choke
switch 115 for detecting that the choke valve C is in an operative
position. The choke switch 115 produces a choke signal j to
indicate that the choke valve C is in the operative position and
therefore the engine idling speed is high. The signal j from the
choke switch 115 is applied to a NOT circuit 120 which produces an
inverted signal j' . The inverted signal j' is at a high level when
the choke valve C is not in the operative position and is applied
to the AND circuit 116.
It will be understood that the AND circuit 116 produces an output k
which becomes high level when all of the input signals g, h, a', i
and j' are at a high level. In other words, when the shift lever
53a is in the D-range and the vehicle is substantially stopped, the
AND circuit 116 produces a high level output k if the engine 2 is
idling and the vehicle brake is applied, except in the engine
warming up period wherein the engine idling speed is high.
Referring to FIG. 3, it will be noted that the output k from the
circuit 111 is applied to the OR circuit 109. Further, the output k
is inverted and applied to the AND circuits 106, 107 and 108.
Therefore, when the output k is at a low level, the gear stage
selection signals d.sub.1 through d.sub.4 are passed to the
solenoid selecting map 110, as they are to thereby select
appropriate ones of the solenoids 71 through 74 as determined by
the circuits 101 and 102. However, when the output k is at a high
level, only the output from the OR circuit 109 is at a high level
so that the fourth gear stage is selected by energizing appropriate
ones of the solenoids 71, 72 and 73. When the vehicle brake is
released to start the vehicle, the output k of the circuit 111
turns to a low level so that the first stage signal d.sub.1 which
is being produced at this instance is now passed through the AND
circuit 106 to the solenoid selecting map 110 to select the first
gear stage. It is therefore possible to start the vehicle smoothly
utilizing the creep phenomenon of the torque converter 10.
When the engine choke valve C is in operation, the choke switch 115
is closed to produce a high level signal j, which ultimately turns
the output k of the circuit 111 to a low level. Therefore, the
first gear stage is selected when the vehicle is substantially
stopped. In parallel with or in lieu of the choke switch 115, there
may be provided a vehicle facility switch such as an air
conditioner switch.
According to the present invention, the control unit 100 can be
provided by a microprocessor with an appropriate program. The
operation will now be described with reference to FIGS. 6 through
13.
General Operation
FIG. 6 shows in general the operation of the control unit. When the
program is initialized at the step A.sub.1, the ports in the
respective hydraulic control valves and the circuit are brought
into initialized positions to thereby hold the gear mechanism at
the first stage and release the torque converter lock-up clutch 17.
Thereafter, the shift range or the position of the select valve 53
is read at the step A.sub.2 and a judgement is carried out in the
step A.sub.3 as to whether the shift range is in the 1-range. If
the judgement is YES, a signal is produced in the step A.sub.4 to
de-energize the solenoid 74 so as to release the lock-up clutch 17.
Then, a calculation is made in the step A.sub.5 to determine
whether the engine will overrun if the gear mechanism is shifted
down to the first stage. A judgement is then made in the step
A.sub.6 as to whether the engine will overrun based on the result
of the calculation in the step A.sub.5. If the judgement is YES, a
signal is produced to shift the gear mechanism to the second stage
in the step A.sub.7. If the judgement in the step A.sub.6 is NO, a
signal is produced to shift the gear mechanism to the first stage
in the step A.sub.8. If the judgement in the step A.sub.3 is NO, a
further judgement is carried out in the step A.sub.9 as to whether
the shift range is at the "2" range. If the judgement is YES, a
signal is applied in the step A.sub.10 to energize the solenoid
valve 74 to release the lock-up clutch 17, and a further signal is
applied in the step A.sub.11 to fix the gear mechanism at the
second stage. If the judgement is to indicate that the shift range
is not at the second stage, it is interpreted that the shift valve
53 is in the "D" range. Then, a judgement is made in the step
A.sub.12 as to whether the vehicle is stopped and, if the result of
the judgement is NO, the shift-up control, the shift-down control
and the lock-up control are carried out, respectively, in the steps
A.sub.13, A.sub.14 and A.sub.15. If the judgement is the step
A.sub.12 is YES, an idle vibration suppress control is carried out
in the step A.sub.16.
Shift-up Control
Referring to FIG. 7, the gear position of the transmission gear
mechanism 20 is at first read and a judgement is made in the step
B.sub.1 as to whether the gear mechanism 20 is at the fourth stage.
If the judgement is YES, the shift-up control is terminated because
no further shift-up is possible. If the fourth gear stage judgement
in the step B.sub.1 is NO, the engine throttle valve position is
read in the step B.sub.2 and a reference turbine speed Tmap is read
in the step B.sub.3 from the selected shift-up control line Mu
which is shown in FIG. 8. Thereafter, the actual turbine speed T is
read in the step B.sub.4 and a judgement is made in the step
B.sub.5 as to whether the actual turbine speed T is greater than
the reference turbine speed Tmap. If the judgement is YES, a
further judgement is made in the step B.sub.6 as to whether the
shift-up flag F.sub.1 is set to zero. If the result of the
judgement is NO, the procedure is terminated but, if the judgement
is YES, the shift-up flag F.sub.1 is set to one in the step B.sub.7
and one stage shift up is carried out in the step B.sub.8 by
appropriately energizing the solenoids 71, 72 and 73.
If the judgement in the step B.sub.5 is NO, a new shift up control
line Mu' is provided as shown in FIG. 8 by multiplying in the step
B.sub.9 the reference turbine speed Tmap with a constant 0.8 to
obtain a new reference speed Tmap. Then, a judgement is made in the
step B.sub.10 as to whether the actual turbine speed T is greater
than the new reference speed Tmap. If the result of the judgement
is YES, the procedure is terminated but, if the judgement is NO,
the shift up flag F.sub.1 is reset to zero in the step B.sub.11.
The steps B.sub.9 through B.sub.11 are performed in order to
prevent the gear shifting operations from being repeatedly carried
out when the turbine speed T is close to the reference turbine
speed Tmap.
Shift Down Control
As shown in FIG. 9, in the gear shift down control, the gear
position of the transmission gear mechanism 20 is at first read and
a judgement is made in the step C.sub.1 as to whether the gear
mechanism is at the first stage. If the judgement is YES, no
further control can be carried out so that the control is
finished.
If the aforementioned judgement is NO, the engine throttle valve
position is read in the step C.sub.2 and a reference turbine speed
Tmap is read in the step C.sub.3 from the selected shift down
control line Md which is shown in FIG. 10. Thereafter, the actual
turbine speed T is read in the step C.sub.4. Then, a judgement is
made in the step C.sub.5 as to whether the actual turbine speed T
is smaller than the reference turbine speed Tmap. If the result of
the judgement is YES, a further judgement is made in the step
C.sub.6 as to whether the shift down flag F.sub.2 is in the zero
position. If the result of the judgement is NO, the procedure is
terminated but, if the result of the judgement is YES, the shift
down flag F.sub.2 is set to one in the step C.sub.7 and a one-stage
shift down is carried out in the step C.sub.8.
If the judgement in the step C.sub.5 is NO, a new shift down
control line Md' is provided as shown in FIG. 10. This is in effect
carried out by dividing in the step C.sub.9 the reference turbine
speed Tmap by a constant 0.8 to obtain a new reference turbine
speed Tmap. Then, a judgement is made in the step C.sub.10 as to
whether the new reference turbine speed Tmap is smaller than the
actual turbine speed. If the result of the judgement is YES, the
procedure is terminated but, if the result of the judgement is NO,
the shift down flag F.sub.2 is reset to zero in the step
C.sub.11.
Lock Up Control
Referring to FIG. 11, the engine throttle valve position is read in
the step D.sub.1 and a reference turbine speed Tmap is read in the
step D.sub.2 from the lock up release line Moff as shown in FIG.
12. Then, the actual turbine speed T is read in the step D.sub.3
and a judgement is made in the step D.sub.4 as to whether the
actual turbine speed T is smaller than the reference turbine speed
Tmap. If the result of the judgement is YES, the step D.sub.5 is
carried out to release the lock-up clutch 17 but, if the result of
the judgement is NO, a further reference turbine speed Tmap is read
in the step D.sub.6 from the lock up engage line Mon. Thereafter, a
judgement is made in the step D.sub.7 as to whether the actual
turbine speed T is greater than the reference turbine speed Tmap.
If the result of the judgement is NO, the procedure is finished. If
the judgement is YES, a signal is produced in the step D.sub.8 to
engage the lock up clutch 17.
Idle Vibration Suppressing
Referring again to FIG. 6, if the judgement in the step A.sub.12
shows that the vehicle is substantially stopped, a process of
suppressing idle vibrations by blocking transmittal of the engine
idle vibrations to the vehicle body. The process is shown in FIG.
13.
When the shift lever 53a is in the D-range and the vehicle is
substantially stopped, a judgement is made in the step E.sub.1 as
to whether the engine throttle valve 2a is opened. If the answer is
YES, the procedure comes to the end but, if the answer is NO, a
further judgement is made in the step E.sub.2 as to whether the
vehicle brake is engaged. If it is judged that the vehicle brake is
not engaged, the procedure comes to the end; however, if the
vehicle brake is engaged, a further judgement is made in the step
E.sub.3 as to whether the choke switch 115 is closed. If the choke
switch is closed, the procedure comes to the end. If the choke
switch 115 is not closed, it is judged that the choke valve C is
not in the operative position and the step E.sub.4 is carried out
to shift up the gear mechanism to the fourth stage.
In the embodiments described above, the gear mechanism is
positioned to the fourth stage to block the transmission of the
engine idle vibrations to the vehicle body; however, it is quite
possible to use another gear stage, for example, the third gear
stage. Further, a similar control may be made when the shift lever
is in another running range, such as the 2-range or the 1-range.
Therefore, it should be construed that the invention is not limited
to the details of the embodiments shown, but changes and
modifications may be made without departing from the scope of the
appended claims.
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